The present invention relates to gas-tight seals and to trocar systems incorporating such seals.
Trocar systems are used during abdominal operations for maintaining a passage through the abdominal wall of a patient. Trocar systems generally comprise a cannula in the form of an elongate tube terminating in an enlarged upper body and an obturator or cutting tool which is fed through the enlarged upper body and down the elongate tube to pierce the abdominal wall so that the elongate tube can follow the tool through the wall. The cutting tool is then removed leaving the way clear for elongate surgical instruments or equipment, such as endoscopes, to be fed into the abdomen through the tube. To provide space within the abdomen, the abdomen is inflated with a gas and this allows easy access to the various organs located within the abdomen. To maintain gas pressure the trocar system is provided with a flap valve which is urged by the pressure of gas into a closed state. The flap valve must, however, be opened to allow the passage of surgical tools. Accordingly a sealing system is provided in the enlarged upper body to provide a seal around the surgical instrument once it has been inserted into the enlarged upper body. This now creates a gas lock between the flap valve and the seal and so the flap valve can now be opened (either by pushing the instrument against it or by other means) substantially without loss of pressure in the abdomen. The instrument can now be fed into the abdomen and manipulated as required. Usually more than one trocar is used so as to provide multiple entry points into the abdomen.
The diameter of the instruments used is usually much smaller than the diameter of the tube or the enlarged body and so a considerable amount of lateral off-axis movement of the instruments can and does take place in order to effect the desired manipulation of the instrument. Because the seals used are static, any movement of the instrument other than axial can to strain the seal to the extent of temporarily breaking the seal and so allowing gas to escape. Also most seals are designed with a specific diameter of instrument in mind and so different seals or adaptors are required when changing instruments.
It is an object of the invention to provide an improved seal.